Build (game engine)
Build (game engine)
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Build (game engine)

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Build (game engine)

The Build Engine is a first-person shooter engine created by Ken Silverman, author of Ken's Labyrinth, for 3D Realms. Like the Doom engine, the Build Engine represents its world on a two-dimensional grid using closed 2D shapes called sectors, and uses simple flat objects called sprites to populate the world geometry with objects.

The Build Engine is generally considered to be a 2.5D engine, as the basic world geometry is two-dimensional with an added height component, allowing each sector to have a different ceiling height and floor height. Some floors can be lower and some can be higher; the same is true with ceilings (in relation to each other). Floors and ceilings can hinge along one of the sector's walls, resulting in a slope. With this information, the Build Engine renders the world in a way that looks three-dimensional, unlike modern game engines that create actual 3D environments.

Though the Build Engine achieved most of its fame from powering the 1996 first-person shooter Duke Nukem 3D, it was also used for many other games.

Sectors are the building blocks of a level's layout, consisting of a two-dimensional polygonal outline when viewed from above, with the top and bottom faces of the sector given separate altitudes to create a three-dimensional space. Hence, all walls are perfectly vertical—anything appearing otherwise is technically a sloped floor or ceiling. The word room can be used as a loose substitute to aid understanding, though one room in the game world can consist of many sectors, and parallaxed skies can give the illusion of being outdoors. Sectors can be manipulated in real-time; all of their attributes such as shape, height, and slope could be modified "on-the-fly" by games, unlike the earlier Doom engine. This allowed games to have destructible environments, such as those seen in Blood. This technique is similar to the use of push walls in the earlier Apogee Software title Rise of the Triad which featured similar dynamic environments.

Developers of games based on the engine used special reserved "sprites" (game objects), often called "sector effectors [sic]", that, when given special tags (numbers with defined meanings), would allow the level designer to construct a dynamic world; similar tag information could be given to the sector walls and floor area to give a sector special characteristics. For example, a particular sector effector may let players fall through the floor if they walk over it and teleport them to another sector; in practice, this could be used to create the effect of falling down a hole to a bigger room or creating a body of water that could be jumped into to explore underwater. A sector could be given a tag that made it behave like an elevator or lift.

Sectors could overlap one another, provided they could not be seen at the same time (if two overlapping sectors were seen at the same time, a hall of mirrors effect resulted). This allowed the designers to create, for instance, air ducts that appeared to extend across the top of another room (however, doing so could be tricky for designers due to the 2D viewpoint used for much of the editing process). This allowed the designers to create worlds that would be physically impossible (e.g. a doorway of a small building could lead into a network of rooms larger than the building itself). While all these made the games using the engine appear to be 3D, it wouldn't be until later first-person shooters, such as Quake, which used the Quake engine, that the engine actually stored the world geometry as true 3D information, making the creation of one area stacked atop another area in a single map very feasible.

Later versions of Ken Silverman's Build Engine allowed game selected art tiles to be replaced by 3D objects made of voxels. This feature appeared too late to be used in Duke Nukem 3D, but was seen in some of the later Build Engine games. Blood uses voxels for weapon and ammo pickups, power-ups, and eye-candy (such as the tombstones in the "Cradle to Grave" level, some chairs, and a crystal ball in "Dark Carnival"). Shadow Warrior makes even more advanced use of the technology, with voxels that can be placed on walls (all of the game's switches and buttons are voxels).

For several years, Ken worked on a modern engine based entirely on voxels, known as Voxlap.

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